Automatic telephone system



Dec. 14 .1926.

B. D. WILLIS AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 1. 1922 3Sheets-Sheet 1 Bernard Dlnfflhs Dec. 14 1926.

1,610,346 B. D. WILLIS AUTOMATI C TELEPHONE SYSTEM flr'iainn'l FilgdlebI 19?? 3 sheet sh t 2 Bernard ,Ulnfflh Z. 424

Dec. 14 1926. 1,610,346

B. D. WILLIS AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 1. 1922' 3Sheets-Sheet 3 Egan! Elam 11; v

fin-

Patented b... 14, 1926.

UNITED STATES PATENT OFFICE.

BERNARD D. WILLIS, OF OAK PARK, ILLINOIS, ASSIGNOR, BY MESNEASSIGNMENTS, TO

AUTOMATIC WARE.

nnncrnrc me, or cnrcaeo," ILLINOIS, A oonronarron or DELA- AU r'oMArIcTELEPHONE SYSTEM.

Application filed February 1,-1922,'Seria1 No. 533,214. Renewed May 3,1926.

The present invention relates to automatic telephone systems in generalbut 1s concerned more particularly with such systems as comprisemain andsubexchanges and the object, briefly'stated, is the provislon of new andimproved circuit arrangements whereby the operation of the holdingcircults employed on sub to main exchange trunks 1s improved andrendered more etficient and.

when placed in order with the correspond-.

ing lines at the ends thereof in alignment, represent by means of theusual circuit diagrams a sufficient amount of apparatus for a completeconnection between a calling subexchange substation and a called mainexchange substation.

Fig. 3 shows a desirable modification of the equipment shown in Fig. 1,which is used when the so called plunger type of line switch is used.

The apparatus shown in Figs. 1 and 3 is assumed to be located in thesubexchange and the apparatus shown in Fig. 2 is assumed to be locatedin the main exchange.

The substations A and A Figs. 1 and 3, I

respectively, are of the usual automatic t e. V

lhe line switch C, Fig. 1, in which the line of substation A terminates,is of the well known rotary type in which the wipers have no normalposition and move in aforward-direction only. The line switch C, Fig. 2,.is an exact duplicate of the line switch The holding circuit D, Fig. 1,is provided primarily for the purpose of permitting the third conductorto be eliminated from the trunk X which extends to the main exchange.Other functions of this device will be explained fully hereinafter.

The selector E, Fig. 2, is mechanically 0fthe well known vertical androtary type in which the bank contacts are arranged in horizontal rowsor levels. The circuit operatlons and functions of such a switch arewell known and consequently they do not need to be dwelt upon-at thistime. The selector F, which is denoted by the dotted rectangle bearingthatreference character, 1s assumed to be an exact duplicate of theselector E with the exception of the additlon of an mcoming releasetrunk conductor whlch is connected to the upper armature-of the releaserelay thereof.

The connector H is mechanically identical with the selector E or theselector F. Most of the circuits of this connector, being old and wellknown, have been omitted, only the line, release, and back bridge relaysbeing shown.

Referring now to Fig. 3, the line switch C shown therein is of the" wellknown plunger type; and the holding circuit D is a modification of theholding circuit D, Fig. 1, as will be pointed out fully hereinafter.

Certain ofthe slow-acting relays such as 15 have a copper slug on thearmature end and are both slow to energize and slow to deenerglze; whileother slow-acting relays such as41 have the slug on the end opposite thearmature, and are only slow to deenerg1ze. This distinction is indicatedin the drawings by showing the slugs on relays such as 15 in solidblack, and the slugson relays such as 41 by section lines.

The apparatus, having been described in general, will now be describedin connection wlth a detailed description of its operation. For thispurpose it will be assumed that the subscriber at substation A, Fig. 1',in the subexchange, desires to converse with the subscriber atsubstation A, Fig. 2, in the main exchange. When the receiver is removedat the calling substation A, a circuit is closed over line conductors 11and 12 for line relay 15 of the line switch C. Line relay 15, uponenergizing, places ground upon private normal conductor 13 at armature20, thereby closing a circuit for switching relay 14 and'stepping magnet21 in series, and at armature 19 connects test wiper 23 to the circuitat apointbetween switching relay 14 andstepping magnet 21.

From this point the 0 eration do ends upon whether the trunk upon whicwipers of the line switch are standing is busy or'idle. If it is idle,switching relay 14 energizes immediately, but if it is busy the saidswitching relay 14 is short circuited by the ground potential which ispresent upon the test contact of the busy trunk, and stepping magnet 21by its buzzer like action advances the wipers 22-24, inclusive, step bystep until they arrive upon the contacts of an 1dle trunk.

Assuming that the trunk comprising conductors 28-30, inclusive, is thefirst one found to be idle, switching relay 14 being no longer shortcircuited after the switch wipers arrive upon contacts 25-27, inclusive,energizes in series with stepping magnet 21 but the said stepping magnet21 does not energize at this time on account of the high resistance ofswitching relay 14. As a result of the energization of switching relay14. it opens the test circuit and preparesthe holding circuit atarmature 17, thereby placing ground upon .release trunk conductor 29 ofthe seized trunk and making the said trunk busy immediately. As afurther result of the energization of switching relay 14, it disconnectsthe incoming line conductors from the winding of line relay 15 and fromground and extends them by way of armatures 16 and 18 and their workingcontacts, wipers 22 and 24, and bank contacts 25 and 27, to theconductors 28 and 30 of the seized trunk. Line relay 43 of the holdingcircuit D and line relay of the selector E, Fig. 2, energizes in serieswith each other. The energization of line relay 60 of the selector Ecloses a circuit for release relay 61, whereupon the said release relay61 energizes, thereby preparing the switch for operation in the usualmanner.

Before going furtherwith the explanation of the operation of the holdingcircuit D, Fig. 1, certain of its functions will be considered in ageneral way. One function of the holding circuit D is to look a callingline switch in its operated position and give a signal to an attendantwhen the said holding circuit is seized, in case the trunk X is open. Asecond function of the holdingcircuit D which logically follows afterthe first named one is to prevent a subscriber from looking his lineswitch in on a trunk by raising his switch hook' just sufficiently toclose the line circuit, thereby operating the line switch C; and thenpermanently opening the line circuit by lowering his switch hook afterhis line switch has been locked in on a trunk and before it has beenunlocked by the subsequent operation of the line and release relays ofthe seized holding circuit.

Another function of this holding circuit is to prevent an accidentalopening of the the line, after the receiver has been removedsufliciently to allow the line to be closed ering lector.

With these functions in; view, the opera-. c tion of the holding circuitD will now he" proceeded with. When the-ground poten-'" tial is placedupon release trunk conductor 29 at armature 17 of switching relay 14- ofthe line switch C, a circuit is closed for relay 41 of the holdingcircuit D byway. of armature 47 of release relay'42 and its" restingcontact. Relay 41, upon energizing, places a multiple ground uponrelease trunk conductor 29 at armature 45, .thereby com pleting theusual holding circuit for switching relay 14 of the. line switch (3 andcompleting. a locking circuit for itself. It will be seen now thatifline and release relays 43 and 42 do not energize, or in other wordsif the trunk X is open, relay 41 will remain energized and the lineswitch C will remain locked on the seized trunk.

In order to give an alarm tov an attendant, relay 41, upon energizing,places ground upon the common alarm conductor 50 at armature 46, therebyclosing a circuit for alarm relay 51 whereupon the said relay energizes;closes a circuit for the lamp L at armature 52; and at armature 53closes a circuit for the alarm buzzer B. The attendant, upon hearing thebuzzer B and noting the lighted condition of the lamp L, may take thenecessary steps to clear the trouble.

It will be observed that when relay 41 energizes to lock the line switchC on the seized trunk resistance 40 is bridged across conductors 28 and30 at armature 44. This is done so that the subscriber cannot leave theline switch locked in on a trunk which'is not open by opening his lineconductors immediately after having closed them.

Another object accomplished by the bridging of the resistance 40 acrossthe conductors 28 and 30 is to prevent the subscriber from accidentallyopening the circuit of line relay 60 of the selector E, while removinghis receiver, after the holding circuit D has been seized.

Assuming now that the trunk line X is not open, in which case linerelays 60 and 43 of the selector E, and trunk circuit D, respectively,energize, as described, upon the seizure of the trunk X. Line relay 43of the hold-- ing circuit D, upon energizing, closes a circuit forrelease relay 42 at armature 48. Release relay 42, upon energizing,opens the circuit of relay 41 at armature 47, at the same time placing amultiple ground upon release trunk conductor 29. Relay 41, upondeenergizing; after a slight interval, opens the alarm circuit atarmature 46, whereupon relay 60 of the selector alarm relay 51deenergizes. It may be said that in the ordinary operation of the systemdeenergization of relay 41 it removes ground from the release trunkconductor 29 at armature 45, leaving the said conductor 29 grounded atarmature 47 of release relay 42. As a still further result of thedeenergization of relay 41, it removes the resistance '40 fromin bridgeof the conductors 28 and 30 at armature 44, thereby leavin the controlof line and of line relay 43 of the holding circuit D with the callinsubscriber. By this time, however, he wil have removed his receiverentirely from the 1 switch hook so that there is no further likeliing 11at springs131 and 132, which lockhood of an accidental opening of theline.

It will be noted that the lower winding of line relay 60 of the selectorE is not connected to ground directly but is lead through the left handwinding of the transformer as+ sociated with the tone machine -T.Consequently, as soon asthe resistance 40, Fig. 1, is removed from inbridge of the conductors 28 and 30, upon the deenergization of relay 41,the calling subscriber hears the tone produced b the tone machine T, nothaving heardit efore on account of the shunting effect of thenoninductive resistance 40, and begins to operate his calling device inaccordance with the various digits in the dcsired number.

The remaining operation, which has to do with the setting up of theconnection is old and will not need-to be explained. Itwill sufiice tosay that,'after the connection is finally extended to the called line byway of second selector F, connector HT, and line switch C, and after thesubscrlber at the called substation A has answered, the two subscribersmay converse with each fother over the talking circuit shown which isoutlined by the heavy conductors. v

After theconversation iscompleted the two subscribers replace theirreceivers.

, When the receiver is replaced atsubstation A the selectors E and F andthe 'connector H are restored to normal position in the usual manner. Inthe subexchange, line relay 43 of the holding circuit D, upondeenergizing, opensthe circuit' of release relay 42 atarmature 48.Release relay 42,- upon' deenergizing, removes ground from release trunkconductor 29 at armaturev 47 whereupon switching relay 14 of the lineswitch C 'deenergizes, thereby restoringcondit-ions in the said lineswitch C to normal. The entire connection is now released and theapparatus used therein is restored to normal 166 from in bridge'of thetrunk conductors,

apparatus s own therein, which corresponds to the apparatus shown inFig. 1, will be exalarm.

plained. The trunliline will be'under stood, extends toa' selector inthe main exchange similar to the selector E, Fig. 2. As-

sumin now that the subscriber at substation .desiresto make a call, acircuit is closed over line conductors'111 and 112 for line relay 114 ofthe line-switchG Upon energizing, line relay 114 closes a circuit forpull in winding 118 whereupon plunger arm 115 and out o armature 116 areoperated.

Plunger. arm 115, upon being operated, through the medium of a plunger(not' ing circuit includes the lower. winding of relay 151 of the holdincircuit'D' and armaturesv 154 and 160. Re ay 1510f the holdin circuit D,upon energizing in series wit holding winding 117, closes a lockingcircuit for itselfat armature 157 which locking circuit includes theresting contact of armature 154 and said armature, and sprin 132 and itsassociated contact. 'As a fu'rt er' result of the energization of relay151 it' places ground upon thecommon' alarm conductor 163 at armature158, thereby operating alarm relay 164'. As a furtherresult of theenergization of relay 151 it places resistance 166 in bridge of theconductors of the seized trunk at armature 156, thereb guarding againsta lockup being caused li y a momentary removal of the receiver or a likecause and preventing preliminaryimpulses, ,in the previously describedmanner. It will be.

seen now that if one of the conductors ofthe trunk X is open, or if lineand release relays 153 and 152 fail to energize, the line switch C willremain locked on the seizedtrunk and the attendant will be given theusual Assuming. now that the conductors of the trunk X are continuous,line relay 153, upon energizing, closes a 'c'ircuit for release relay-152 at armature 162. Release relay 152, upon energizing, removes theinitial ground potential from release trunk conductor 138 and placesdirect'ground thereon at armature1'60, and opens the alarm circuitat'armature 161. Relay 150, upon energizing in multiple with releaserelay 152, opens its initial circuit and closes a locking circuit foritself, including spring 132 and contact 136 at'armature 155. As afurther resultof the I energization of relay 150, it opens the circuitof relay 151 at armature 154. Relay 151, upon deenergizing, removesresistance thereby leaving'the, control of the connection with thecalling subscriberand permitting him to hear the trunk tone placed onthe line by the selector towhich the trunk X" extends. When the callingsubscriber replaces his receiver, after having called his number, thecircuit of line relay 153 is opened and the said relay, upondeenergizing, opens the cir cuit of release relay 15f. at armature 162.Release relay 152, upon deenergizing, removes ground from release trunkconductor 138 at armature 1G0, whereupon the plunger arm 115 of the lineswitch C is withdrawn and cut off armature 116 restores. In response tospring 132 breaking away 'from contact 136, relay 150 deenergizes,thereby connecting its winding in multiple with release relay 152 atarmature 155' and prepar ing a circuit for relay 151 atarmature 154;.The line switch CF and the holding circuit D are now in normalcondition.

The various features of the invention, having been. described andascertained, will now be pointed out in the following claims.

What is claimed is:

1. In a telephone system, an automatic switch, a trunk line terminatingin said switch, a line relay in said switch bridged across the saidtrunk line, means for extending a calling line to said trunk line, meansat the exchange for automatically completing a circuit for said relayover a talking conductor of said trunk to energize thesaid relayindependent of the calling line, a second relay connected in the saidtrunk in series with said line relay, and means con-'-- trolled by said;second relay for opening 1 said circuit.

2. In a telephone system, a calling line and a called line, a switchcontrolling device on said calling line, means including a subscribercontrolled automaticswitch for extending aconnection from said callingline to 'said called line, means responsive to an initiation of a callby a subscriber on said calling line for connecting said calling lineand said switch together whereby said. switch is placed under thecontrol of said switch controlling device, 'means at the exchange forclosing a temporary shunt around said switch controlling device, andmeans for notifying the calling subscriber when said shunt is opened.

3. In a telephone system, a calling and a called line, means including"a subscriber controlled automatic switch for extending a connection fromsaid calling line to said called line, means responsive to theinitiation of a call by a subscriber on said calling line for connectingsaid calling line and said 1 ended.

over said switch ineffective for an interval, and means for givmg thecalling subscriber a distinctive tone when said interval is connectionfrom said calling line to said called line, means responsive to theinitiation of a call by a subscriber on sand callm line forconnecting'sald calling line and sai switch together and for placingsaid switch under the control of the subscriber on the calling line,means for rendering the control of the subscriber over said switchinefiective, means for rendering said last named means inoperative, andmeans .for notifying the calling subscriber when said switch is againplaced under his control.

5. In a telephone system, a calling line trunk lines, an automaticswitch controlle over the calling line to connect the same with an idletrunk line, a locking circuit for retaining'said switch in operatedposition established responsive to the completion of the connection withthe selected trunk, and means operated automatically and independent ofthe callinglinc for opening said locking circuit. v

(3. In a telephone system, a calling line, trunk lines, an automaticswitch controlled over the calling line to connect the same with an idletrunk line, a locking circuit for retaining said switch in operatedposition established responsive to the completion of the connection withthe selected trunk, a relay connected to each trunk,'means for closing alocal energizing circuit forthe why associated with the trunk in use,and means controlled by said relay for opening said associated with theselected trunk, a holding circuit for said switch closed after saidlockmg circult, means for openmg said locking circuit when the holdingcircuit is closed, a

relay controlling the closure'of said holding circuit, and acircuit forsaid relay including a talking conductor of the trunk but excluding bothconductors of the calling line.

8. In -a telephone system, an automatic trunk selecting switch havingmovable contacts, trunk lines accessibleto said switch and terminatingin fixed contacts, means for operating said switch to select and connectwith an idle trunk, a locking circuit for retaining said switch inoperated position established automatically responsive to the engagementof a non-talking movable contact of said switch with a fixed contactassociated with the selected trunk, a relay'for closing said lockingcircuit, contacts on said relay for closing a bridge across the talkingconductors of the selected trunk, and meansresponsive to the closure ofsaid bridge for opening said locking circuit.

9. .In a telephone system, an automatic trunk selecting switch havingmovable contacts, trunk lines accessible to said switch and terminatingin fixed contacts, means controlled over a calling line for operatingsaid switch to select and connect with an idle trunk, a locking circuitfor holding said switch in operated positionincluding a movable switchcontact and a fixed contact associatedwith the selected trunk, meansinitially controlled over the selected trunk alone for closinga holdingcircuit to retain said switch in operated position, said last meanscontrolled thereafter over the calling line and trunk in series, andmeans for opening said locking circuit after the said hold ing circuitis closed.

10. In a telephone system, a sub-exchange trunk line including twotalking conductors and a local third conductor, subscribers in dividualline switches in the sub-exchange having access to said trunk line,means controlled over a calling line for operatin one of said switchesto connect with said trunk, relay equipment in said trunk line adaptedto complete a holding circuit for the operated line switch, a lockingcircuit including the third conductor of said trunk established when thetrunk is connected with for retaining the switch in operated until thesaid holding circuit is esta lished, and means for initially operatingsaid relay equipment independent of the callingv line.

11. In a telephone system, a trunk huntmg a calling subscriber throughthe-medium of sa d relay for operating said switch to seize said trunk,means independent of the calling subscriber for locking said switch onsaidtrunk res onsive to the seizure thereof, and

trunk lines, a rotary line switch controlled over the calhng hne toconnect the same withan idle trunk line, a locking circuit for retam ngsald switch in operated position establlshed responslve'to thecompletion of a osition switch comprising a rel'ay, a trunk,accessibleto said switch, means controlled by connection with the selected trunk,said 'circuit including 'axwiper of said line switch, andmeans operatedautomatically and independent of the calling line for opening saidlocking circuit.

13. In a telephone systein,"a calling line,

trunk lines, a rotary line switch controlled over the calling line toconnect the-same with an idle trunk line, a locking circuit forretaining said switch in operated position es-f tablished responsive tothe'completion of a accessible to said switch terminatin in fixedcontacts, means controlled over a ca 1ngl1ne for operating said switchto connect with an idle trunk, a relay in said trunk, a lockinge circuitfor holding said switch inoperate position established responsive tojthecom:

.pletion of a; connection with the said trunk, said circuit includingtwo movable switch contacts, two fixed contacts associated .w1th

said trunk, and a winding of said-relay in series, and contacts on'saidrelay forqclosing abridge across the talking conductors of said trunks.

15. In a telephone system,'anautomatic Switch having movable contacts,trunk lines accessible to said switch and terminating in fixed contacts,means controlled over a calling line for operating said switch toconnect with an idle trunk, a locking circuit for holdingsaid switch inoperated position estaba lished, automatically when the trunkisconnected with, said circuit including two move-' able contacts and twofixed contacts -asso' ,ciated with said trunk, a holding'circuit of saidswitch including only one of said 'moveable and one of said fixedcontacts, andity of the calling line for closing ing' circuit and foropening said 7 cult.

In witness whereof, I hereunto subscribe my name this twentieth day ofJanuary, A. 'D. 1922.;

BERNARD D. WILLIS.

'means operated independent of the continuv -v said hold-

